The present invention relates to an offset printer for printing annular codes of colours on solids of revolution and more particularly on small solids of revolution like connector contacts or necks of ampoules in which the colour is applied to a common inking cylinder by means of rotative discs.
There exists a more and more increasing need for identifying small solids of revolution, e.g. connector contacts or contact pins of small dimensions for electronic components and the like by marking them with annular codes of colours. With a view to the small dimensions of such parts having e.g. an available printable surface of 1 mm in diameter and 3 to 4 mm in length it is required to provide clean, sharp limited printings of relativ narrow colour rings. Tests have shown that the offset printing of small parts with clean rings of colour leads to particular difficulties because it is particularly not easy to deposit the colour on the inking cylinder in a sufficiently clean manner.
It is accordingly the object of the present invention to realize an offset printer which permits to deposit clean, sharp delimited annular codes of colours on very small solids of revolution. It has been determined that the above mentionned difficulties are due to the fact that during the transfer of the colour from the colour chambers to the inking cylinder, the colour is not cleanly enough stripped off from the relative discs. It has been further discovered that the reason for this defect is that with a rigid arrangement of the discs and the colour chambers it is impossible to realize a close enough fitting of the discs with respect to the axial limitations of the slit through which the discs enter the colour chambers.